It won't happen in the next year, that's for sure. The 3DS is just starting to take off. Once the economy improves and the 3DS gets another price cut, I doubt the PSVita will catch it. Look at the PSP. It finally started to take off a bit, but now the games are drying up and Sony is ready to dump it for the PSVita. Surprisingly, the PSP has been outselling the PSVita during the holidays. I honestly don't expect the PSVita to take off until the price of the unit and the memory card drop significantly. That won't happen for at least 18-24 months from now. I don't see it beating the 3DS or DS.
__________________________________________
'gaming till I'm gone'